Method and apparatus for applying a plastic spacer onto a glass panel

ABSTRACT

A method and apparatus for applying a plastic strand (35), as a spacer with a predefined intended thickness (D), onto a glass panel (33) in order to constitute insulating glass panes, by means of a nozzle (17) which is moved along the edge of the glass panel (33) around the latter and thereby deposits the strand (35) emerging from the nozzle (17) onto the glass panel (33) so that the beginning and end of the strand (35) abut one another. The thickness of the strand (35) upon emergence from the nozzle (17) is increased, at the beginning of a segment with a defined length (L), from zero to the intended thickness (D); and in complementary fashion thereto, at the end of the strand (35) is decreased over the same length from the intended thickness (D) to zero.

BACKGROUND OF THE INVENTION

It is known in the assembly of insulating glass panes whose glass panelsare held apart and adhered to one another by a plastic spacer, first toapply the strand-like spacer onto a first of the two glass panels alongits edge, such that a gap remains between the ends of the spacer in thevicinity of a corner of the glass panel, and is not closed until later,after assembly and pressing of the insulating glass pane. Closing mustbe performed very carefully so as not to leave open any gap throughwhich moisture might penetrate into the interior of the insulating glasspane. It is known to close the gap by passing a heated shaped elementaround that end of the plastic spacer at which the gap is located, sothat the thermoplastic material of which the spacer is made softens, andthe two ends of the strand of which it is constituted join one anotherto form a continuous frame. This entails problems in practicalimplementation, however: the abutting surfaces between the two ends ofthe spacer cannot be reached with the heated shaped element, and it isalso difficult to exert pressure thereon because it is possible to acton the spacer only from outside, i.e. parallel to the abutting surfaces.It becomes particularly difficult to close the gap when it is notalready quite narrow, since then the action of a heated shaped elementalone is not sufficient, and instead additional thermoplastic materialmust be introduced into the gap, which is difficult and moreover leadsto a disturbingly obvious and unattractive join between the two ends ofthe spacer. In this case the join also remains a weak point in theotherwise reliable seal of the interior of the insulating glass pane.

It is known to close the gap in a plastic spacer, located in thevicinity of a corner, even before the insulating glass pane isassembled, by acting on the corner from both the inside and the twoouter sides with three separately movable shaped elements. This yields abetter join between the two ends of the spacer, but with considerablecomplexity in terms of equipment and above all time, which leads to alengthening of the cycle time of the apparatus which applies the spaceronto the glass panel.

In the case of both procedures known from the related art, it isdisadvantageous that the gap initially existing between the ends of thespacer is not reproducible, since irregularly shaped abutting surfaceswith varying spacing are formed.

SUMMARY OF THE INVENTION

It is the object of the present invention to indicate a way in which, inthe application of an in-situ extruded strand to form a plastic spacer,the beginning and end of the strand can be joined to one another moreeasily, more rapidly, and more reliably.

According to the invention, the plastic strand provided as the spacer isextruded by means of a nozzle, and applied onto the glass panel, in sucha way that the beginning and end of the strand meet one another not inblunt fashion, but rather by way of an oblique surface which is formedby the fact that the thickness of the strand upon emergence from thenozzle is increased, at the beginning of a segment with a definedlength, from zero to the intended thickness of the strand; and incomplementary fashion thereto, at the end of the strand is decreasedover the same length from the intended thickness to zero, which can beachieved by means of a nozzle whose outlet cross section is modifiableand which, while it is being moved along on a glass panel, can be liftedaway from it. Even with this procedure, a gap unavoidably resultsbetween the beginning and end of the strand, but this gap is placedunder pressure when the insulating glass pane is assembled, since it isabsolutely necessary and usual to press insulating glass panes, on theone hand in order to achieve the desired intended thickness of theinsulating glass pane, and on the other hand to guarantee a permanentjoin, sealed against water vapor diffusion, between the sides of theplastic spacer and the adjacent glass panels. This pressing necessarilyalso presses together the two oblique surfaces at the beginning and endof the strand, and joins them sealedly together without further action.In contrast to the related art it is not necessary to act subsequentlyon the join with any kind of mechanical, heated devices; theequipment-related outlay associated therewith is completely eliminated,and closing of the spacer requires no additional processing time, i.e.has no influence on the cycle time of an insulating glass productionline. The economic advantage of the invention is therefore considerable.

The desired sealed pressing of the two oblique abutting surfaces ispromoted if the upper side of the extruded strand is configured with aslight convexity and/or if, at the abutting point between beginning andend of the strand, the end section located on the oblique beginningsection slightly exceeds the intended thickness of the strand on itsupper side, so that pressing of the spacer in the region of the abuttingpoint automatically acts somewhat more strongly than in the remainingarea of the spacer. The segment over which the abutting point extends isadvantageously between 3 and 12 cm long; in initial experiments, alength of 8 to 10 cm has proven particularly suitable.

The apparatus according to the invention has a nozzle having asubstantially rectangular outlet cross section which determines thecross-sectional shape of the emerging strand, and a slide valve whichcan close off the outlet opening of the nozzle and for that purpose isequipped with a first drive system which can impart to the slide valve adefined, reproducible displacement motion. A second drive system isprovided to move the nozzle in a plane, specifically parallel to theflat glass panel; this can be a conventional X-Y drive system which canmove the nozzle in two mutually perpendicular directions, in combinationwith a rotary drive system which makes it possible to reorient thenozzle at the corners through 90 degrees or, in the case of so-calledmolded panes, to follow the curved edge of a glass panel. It would alsobe possible, however, to provide instead of the X-Y drive system, adrive system that allows displacement of the nozzle in only onedirection, if, in combination therewith, the glass panel is displaceablein its plane perpendicular to the displacement direction of the nozzle.Lastly, a third drive system is also provided to move the nozzletransverse to the plane of the glass panel in order to be able to liftthe nozzle in controlled fashion when the end section of the strand,which is deposited on the wedge-shaped beginning section of the strand,is extruded. In order to diminish the strand cross section duringremoval of the nozzle from the glass panel, corresponding to theincreasing distance, the drive system for actuation of the slide valveand the drive system for removal of the nozzle from the glass panel aresynchronized with one another. Synchronization can be accomplished bydriving a mechanical branching drive train using a shared motor.Electronic synchronization of two separate motors is, however, moreelegant.

The outlet opening of the nozzle could be directed obliquely against theglass panel surface. It is more favorable for the movement sequence andthe uniformity of the strand deposited onto the glass panel, however, ifthe outlet opening of the nozzle extends at right angles to the plane ofthe glass panel, and the movement direction of the nozzle is in theopposite direction. In this context the edge that necessarily existsbetween the outlet opening of the nozzle and the glass panel should beas narrow as possible so that the outlet opening can be brought as closeas possible to the glass panel. While depositing the strand, the nozzlecan slide on the glass panel with the end surface adjacent to the outletopening. As soon as the nozzle has arrived back at the wedge-shapedbeginning section of the strand that it has deposited, it is graduallylifted, the lifting being synchronized with the simultaneously occurringclosing of the nozzle and being matched to the speed of the motionparallel to the glass panel plane so that a wedge-shaped end section ofthe strand is produced which has a shape complementary to the beginningsection, so that the beginning section and end section have a thicknesswhich is the same as or somewhat greater than the thickness of thestrand outside the abutting point. To allow the nozzle to moveunimpededly over the wedgeshaped beginning section of the strand, theend surface of the nozzle facing the glass panel plane is preferablyoriented in similar fashion obliquely with respect to the glass panelplane, the angle of inclination with respect to the glass panel planepreferably being somewhat greater than is produced in the case of theoblique surface of the wedge-shaped beginning section of the strand. Anoblique surface of this kind at the tip of the nozzle body is not,however, absolutely necessary; it would instead also be possible toinitiate a rotary motion of the nozzle by means of which the outletopening is gradually faced toward the glass panel plane, but such asolution would be more complex and less elegant.

The slide valve should preferably have a sharp leading edge so theemerging strand can be easily delimited and ultimately capped. If thisleading edge has a slight concave curve and thus produces a slightlyconvexly curved surface on the strand, this is advantageous foreffective pressing of the abutting point and sealing of the insulatingglass pane when it is assembled.

DESCRIPTION OF THE DETAILED DRAWINGS

The appended schematic drawings provide additional explanation of theinvention.

FIG. 1 shows an apparatus according to the invention in a front view;

FIG. 2 shows the same apparatus in a partially sectioned side view;

FIG. 3 shows a longitudinal section through the nozzle of the apparatus;and

FIGS. 4 to 7 show the nozzle in four different phases of the productionof a plastic spacer on a glass panel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2 apparatus of the invention has a carrier 1which can be displaced along a crossmember 2 by a drive system 3,perpendicular to the drawing plane of FIG. 2. The crossmember itself isparallel to a plane 4 in which, during processing, the surface of aglass panel lies, displaceably at right angles to the longitudinalextension of crossmember 2. Also mounted on carrier 1 is a block 5 whichcan be pivoted by a rotation cylinder 6 about an axis 7 that is parallelto plane 4 and lies in the drawing plane of FIG. 2, and can be displacedperpendicular to plane 4 by a drive system consisting of an electricmotor 8 and a spindle 9. In order to be able to perform this motion incontrollable steps and at a controllable speed, motor 8 is connected toa rotor position and speed transducer 10.

Block 5 carries two alternatingly operated, refillable piston-cylinderunits 11 and 12 to store and dispense the plastic compound from whichspacers are to be formed. Piston-cylinder units 11 and 12 are eachequipped with a level indicator 13, 14 with limit switches. The twopiston-cylinder units 11 and 12 stand on a common valve block 15 intowhich a heated pressure hose 16, through which the plastic compound issupplied to the cylinder, opens.

Located in valve block 15 is a rotary slide valve which alternatinglyconnects the one piston-cylinder unit 11 or 12 to pressure hose 16, andthe other piston-cylinder unit 12 or 11 to a nozzle 17. The nozzle islocated at the tip of a hollow nozzle shaft 18 which is mountedrotatably in a mount 19 in which, via a rotary coupling known in theart, the plastic material forced out of one of piston-cylinder units 11,12 passes into hollow nozzle shaft 18.

To rotate nozzle shaft 18 in its mount 19, a rotary drive system 20 witha slip ring transfer unit 21 and a rotor position and speed transducer22 are attached to block 5.

Nozzle 17 has an end surface 23, running obliquely with respect to plane4, which tapers to a point and immediately delimits an outlet opening 24of the nozzle oriented perpendicular to plane 4. Outlet opening 24 has asubstantially rectangular cross section. Rotation axis 25 of nozzleshaft 18 extends in the center of the outlet opening.

A slide valve 26, shown in FIG. 3, is arranged replaceably between awall 27 of the nozzle shaft running parallel to axis 25 and a removableretainer 28, and is provided to close off outlet opening 24. Slide valve26 is guided displaceably, parallel to axis 25, between wall 27 andretainer 28. In order to displace it, it is equipped with teeth 29 whichmesh with a pinion 30 that can be driven controllably by a smallelectric motor installed on nozzle shaft 18. The slide valve positioncan be influenced by a potentiometer 32, shown in FIG. 1.

Electric motor 31 and motor 8 are electronically synchronized with oneanother.

Reference is now made to FIGS. 5 to 7 in order to explain the operationof the apparatus.

A glass panel 33, on whose upper side a plastic strand is to be appliedas a spacer, lies with its upper side in plane 4, which is indicated inFIGS. 1 to 3. Nozzle 17 is lowered onto said upper side 4 (FIG. 4) byactuation of motor 8, slide valve 26 initially being in a closedposition. The nozzle is then moved, by movement along crossmember 2and/or by movement of crossmember 2 parallel to glass panel 33, in thedirection of arrow 34 in a direction opposite to that of outlet opening24. In the starting phase of the motion, slide valve is gradually openedover a segment of length L, until it reaches a predefined position (FIG.5) in which strand 35 emerging from nozzle 17 has its intended thicknessD. Because of the gradual opening of slide valve 26, strand 35 receivesa gradually increasing thickness in the starting phase along length L,so that the upper side of the strand there is constituted by an obliquesurface 36.

Nozzle 17 is then guided, parallel to glass panel 33 and along its rim,around glass panel 33, thereby depositing onto glass panel 33 a strandof consistent cross section and consistent thickness D. Nozzle 17finally approaches its original position again (FIG. 6). It continuesits movement unchanged until with its lower edge 37 it reaches tip 38 ofthe beginning section of strand 35. Because of the oblique profile ofthe lower end surface 23 of the nozzle, the angle of which is selectedto be somewhat greater than the angle between oblique surface 36 andglass panel 33, planar contact does not occur between lower end surface23 and oblique surface 36. As the movement of nozzle 17 in the directionof arrow 34 continues, the nozzle is now lifted up in controlledfashion, by actuation of motor 8, so that its lower edge 37 moves alongoblique surface 36. Simultaneously and synchronously therewith, slidevalve 26 is gradually advanced; it closes off the outlet opening whenlower edge 37 of the nozzle has reached upper tip 39 of oblique surface36 (FIG. 7). This forms a wedge-shaped end section 40 of the strand,which is configured in complementary fashion to the beginning section ofthe strand and rests on it. Preferably end section 40 is applied in theregion of segment L with slight excess height as compared to intendedthickness D of the strand, so as to obtain a particularly reliable bondin the region of the strand abutting point when the insulating glasspane is later pressed. This excess height can easily be achieved by notbeginning the closing movement of slide valve 26 until lower edge 37 ofthe nozzle has already passed over a short length of tip 38 of thebeginning section of strand 35.

I claim:
 1. A method for applying a plastic material in strand form tocreate a spacer around a perimeter of a glass panel using an apparatushaving thereon a movable nozzle defined by an end surface that defines asubstantially rectangular nozzle outlet opening for dispensing saidplastic material, said apparatus including a respective means for movingsaid nozzle parallel and perpendicular to said glass panel, said nozzleincluding a means for controlling a flow of plastic material from saidnozzle, said strand having a first end, a second end, and a thicknessequivalent to a predetermined distance from a surface of the glasspanel, comprising the steps of:positioning a glass panel adjacent saidapparatus such that said nozzle is disposed in a starting positionadjacent a perimeter edge of the glass panel; simultaneously initiatingmovement of said nozzle along said perimeter with said nozzle outletopening facing away from said moving direction and gradually openingsaid nozzle flow control means from a closed position to a fully openedposition so as to discharge an amount of said plastic material from saidnozzle outlet opening, thereby forming said first end of said strand,wherein when said nozzle moves and dispenses said plastic material, saidnozzle remains close to said glass surface and forms said first end ofsaid strand as a cross-sectionally shaped wedge having a constant widthand a sloping height respective of a surface of a glass panel, whichsaid sloping height defines an oblique surface having a first extent,said height sloping from a surface of said glass panel to a distanceequivalent to said predetermined thickness; continuing manipulation ofsaid nozzle moving means so as to move said nozzle beyond said formedfirst end and to follow a remainder of the perimeter of said glass panewhile simultaneously applying a continuous strand of said plasticmaterial to said glass pane until said nozzle returns to said startingposition and said first end of said strand, said continuous strandhaving a cross-sectional configuration having a constant height andwidth, wherein said constant height is equal to said predeterminedheight, and said constant width is equal to said width of said firstend; gradually closing said nozzle flow control means while continuingthe movement along said perimeter of said panel so as to graduallydecrease the amount of discharge of said plastic material from saidnozzle outlet opening while simultaneously moving said nozzle away fromsaid glass pane in a gradually increasing manner to thereby form asecond end of said strand, wherein said second end of said strand restscoextensively upon said first end and is formed as a secondcross-sectionally shaped wedge complementarily configured to that ofsaid first end, said second wedge having a constant width and a slopingheight, which said sloping height defines a second oblique surfacerespective said surface of said glass pane, said second oblique surfacecomplementary to said oblique surface of said first end, each of saidsurfaces having a generally equal extent.
 2. The method as defined inclaim 1, wherein the strand is configured with a slight convexity on anouter, upper surface thereof.
 3. The method as defined in claim 1,wherein at an abutting point between the first end and the second end ofthe strand, the thickness of the second end of the strand nominallyexceeds the predetermined thickness of the strand.
 4. An apparatus forapplying a plastic spacer strand onto a glass panel to be used forassembling insulating glass panes, comprising:a nozzle having an endthat defines a substantially rectangular outlet opening and a slidevalve for closing the outlet opening; a first drive system for actuationof the slide valve; a second drive system for moving the nozzle in aplane parallel to a glass panel to be operated upon; and a third drivesystem for moving the nozzle transverse to said plane the first drivesystem and the third drive system being synchronized with one another,wherein when said third drive system moves said nozzle away from a glasspanel to be operated upon, the first drive system will close said slidevalve.
 5. The apparatus as defined in claim 4, wherein the outletopening of the nozzle extends at a right angle to a glass panel to beoperated upon, said outlet opening directed opposite to the movementdirection of the nozzle in which it is movable by the second drivesystem.
 6. The apparatus as defined in claim 5, wherein said nozzle hasan end surface, which extends obliquely with respect to a panel to beoperated upon.
 7. The apparatus as defined in claim 4, wherein the slidevalve has a lower edge formed with a slight concave curvature thereon.8. The apparatus as defined in claim 5, wherein the slide valve has alower edge formed with a slight concave curvature thereon.
 9. Theapparatus as defined in claim 6, wherein the slide valve has a loweredge formed with a slight curvature thereon.